Feature Request: Add Edge TTS support

Summary

I'd like to request adding Edge TTS as a new TTS provider in OpenClaw.

Current State

Currently, OpenClaw only supports three TTS providers:

1. Piper
2. Windows (built-in)
3. ElevenLabs

Feature Request

I would love to see Edge TTS (Microsoft Azure's free speech synthesis API) added as a fourth provider.

Benefits

• No API Key required — completely free to use
• High quality natural voices, including popular Chinese voices such as:
  • Xiaoxiao (晓晓)
  • Yunyang (云扬)
  • Yunxi (云希)
• Easy integration — Edge TTS is widely used in the open-source community with mature libraries available (e.g., edge-tts for Python)
• No additional cost for users who want high-quality TTS without subscribing to paid services like ElevenLabs

Proposed Implementation

Add an edge TTS provider option alongside the existing piper, windows, and elevenlabs providers. The implementation could leverage existing open-source Edge TTS libraries to handle the WebSocket-based communication with Microsoft's speech service.

Use Case

This would be especially valuable for users who need natural-sounding Chinese text-to-speech without incurring costs, bridging the gap between the basic Windows built-in voices and the premium ElevenLabs voices.

Start by locating the existing piper, windows, and elevenlabs TTS provider implementations and the provider-selection entry point. Review how those providers are configured and tested, then verify that an edge provider can use Edge TTS voices, including Chinese voices, without an API key and that the new option produces speech successfully.